One hundred patients with Ph1-chromosome-positive chronic myelogenous leukemia (CML) with t(9;22) are included in the present investigation. The position of the Ph1 chromosome in relation to the normal as well as the abnormal chromosomes 9 was localized at metaphase in 1,000 bone-marrow cells. Our study suggests that the rearranged chromosomes, i.e., Ph1 and t(9;22), are closer together than their normal homologues. This impression is based on extensive statistical analysis. The intimate relationship may be due to the fact that they carry reciprocal genetic material responsible for a power of attraction between them. Alternatively, it is tempting to hypothesize that there may be a DNA sequence homology in the bands of chromosomes 9q and 22q involved in the reciprocal translocation perpetuating this relationship in subsequently generating cells during mitotic cell divisions. Furthermore, c-abl and bcr genes might play some role in maintaining the spatial relationship.